History NightmareFuel / CellsAtWork

* ''Staphylococcus aureus'', basically queen of the germs: she knew how to evade the Neutrophils because she mutated into a smarter, deadlier strain after clashing with them before, she set the stage for other opportunistic bacterium to ZergRush a wound, and [[FridgeHorror she's a perfectly normal part of the skin's microbiome.]] But you probably already heard of her before from smash hits like staph infections, bacterial meningitis, and MRSA.

** His backstory is even worse: he had been a blastocyte with genetic mutations, so he started off already scared of being hunted down and viciously beaten to death by authoritarian police for the sole crime of being born, even though he's still a part of the body just like everyone else.
* The hypovolemic shock incident. Imagine the aforementioned scrape, but worse in every way. Millions of erythrocytes are MIA and/or killed, ordinary cells slowly choke to death because they can neither receive oxygen nor get rid of CO2 without those red blood cells, and leukocytes are overwhelmed with wave after wave of opportunistic infections trying to raid the body. Things end well thanks to a last-minute blood transfusion, but it's still the only time in the series that the body and their cells have been close to death, something that not even [[KnightOfCerebus Cancer Cell]] managed to do.

** The anime adaptation conveys this futility dauntingly well. After the emergency broadcast, we see everyone, from the Red Blood Cells to the Killer T-Cells to the Platelets, reluctantly steel themselves for what needs to be done as they prepare to face it. The next two scenes are of AE-3803, her kouhai, and U-1146 combing through the wounded area. The music is gone. A bustling city is completely deserted. [[NothingIsScarier Nobody is here]]. And in the background, as U-1146 stares on in stunned horror, the heartbeat gets louder and faster.

** The anime adaptation conveys this futility dauntingly well. After the emergency broadcast, we see everyone, from the Red Blood Cells to the Killer T-Cells to the Platelets, reluctantly steel themselves for what needs to be done as they prepare to face it. The next two scenes are of AE-3803, her kouhai, and U-1146 combing through the wounded area. The music is gone. A bustling city is completely deserted. [[NothingIsScarier Nobody is here]]. And in the background, a heartbeat pounds away in vain.